Propylene polymers and products thereof

ABSTRACT

The present invention concerns nucleated propylene polymers having a xylene soluble fraction at 23° C. of less than 2.5%, a crystallization temperature of over 124 ° C. and a tensile modulus of greater than 2,000 MPa. These polymers can be prepared by nucleating a propylene polymer with a polymeric nucleating agent containing vinyl compound units, and by polymerizing propylene optionally with comonomers in the presence of a Ziegler-Natta catalyst system primarily transesterified with a phthalic acid ester—a lower alcohol pair to provide said propylene polymer. The catalyst contains a strongly coordinating external donor.

This application is the national phase under 35 U.S.C. §371 of PCTInternational Application No. PCT/FI98/00 867 which has an Internationalfiling date of Nov. 9, 1998, which designated the United States ofAmerica.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to propylene polymers. In particular, thepresent invention concerns efficiently nucleated propylene homo- andcopolymers. The invention further concerns a process for preparing suchcompositions. Finally, the present invention relates to the use of thenew propylene polymers for the manufacture of products by, e.g.,extrusion, blow moulding, thermoforming and injection moulding. Examplesof such articles are tubes, pipes and fittings, housings of variousappliances and cups and pails.

2. Description of Related Art

Propylene (PP) homo- and copolymers have excellent resistance to heatand chemicals as well as attractive mechanical properties. Thesecharacteristics make propylene polymers more suitable than polyethylenefor some uses, for example in pipes, fittings and other similar articlesformed by extrusion or moulding. However, processing of polypropyleneby, e.g., injection moulding, thermoforming or blow moulding, to formthin-walled containers has resulted in products having insufficientstiffness, transparency and cycle time. This is caused by thesemi-crystalline nature of polypropylene. Injection moulding processinghas also resulted in products having insufficient stiffness and cycletime.

In the prior art it has been proposed to improve the transparency ofmoulded polypropylene by blending the polymer with various nucleatingagents such as dibenzilidene sorbitol (DBS), sodium benzoate ordi(alkylbenzilidene)sorbitol. These traditional nucleating agents tendto bleed out from the polymer composition during processing and many ofthem give rise to fumes with an offensive smell. As a solution to theseproblems, it has been suggested in the art to use vinyl compounds, suchas polymers of vinyl cycloalkanes and 3-methyl-1-butene, as nucleatingagents in the form of propylene copolymers or polypropylene compounds,cf. EP Patent Specifications Nos. 0 151 883, 0 152 701, 0 206 515, 0 368577 0 369 658 and 0 417 319. However, the known polymerically nucleatedpolypropylenes still have somewhat low isotacticity and the yield andproductivity of the known polymerization processes are not satisfactory.Further, there is no suggestion in the afore-mentioned EP Patents thatthese polymers would be suitable for manufacture of pipes and fittings.

SUMMARY OF THE INVENTION

It is an object of the present invention to eliminate the problemsrelated to the prior art and to provide a novel high crystallinitypropylene polymer having high isotacticity and excellent mechanicalproperties.

A second object of the invention is to provide a novel process with highproductivity for preparing novel propylene polymer compositions of theabove kind.

It is still a further object of the present invention to provideextruded and moulded products comprising high crystallinity propylenepolymer compositions.

These and other objects, together with the advantages thereof over knownprocesses and products, which shall become apparent from thespecification which follows, are accomplished by the invention ashereinafter described and claimed.

The invention is based on the idea of providing a propylene polymerwhich is nucleated with 0.0001 to 1% by weight of a polymerized vinylcompound and containing less than 0.01 wt-ppm (or below the limit ofdetection of the Gas Chromatography-Mass Spectrometry, GC-MS, method) ofunreacted monomeric vinyl compounds. Polymerization of propyleneoptionally with comonomers in the presence of a transesterifiedZiegler-Natta catalyst system comprising a strongly coordinatingexternal donor will yield a nucleated polymer of the above kind havingimproved isotacticity. Thus, homopolymers prepared with a ZN catalystsystem modified with a polymerized vinyl compound will have a content ofless than 2.5%, in particular less than 2% xylene solubles at 23° C., acrystallization temperature of over 124° C., in particular 126° C. orhigher, and a tensile modulus of greater than 2,000 MPa, preferablygreater than 2,100 MPa (or even greater than 2,200 MPa). By using amodified catalyst composition containing practically no or only minuteamounts (preferably less than 2000 ppm, in particular less than 1000 ppmof monomer residues ) for the manufacture of the propylene polymer, noseparate washing steps are needed and high catalyst activity can bemaintained.

Finally, it has now been observed that high polymerization temperatureincreases isotacticity. Thus, the amount of xylene solubles decreaseswith 20 to 25% or more when the polymerization temperature is increasedfrom 70° C. to 90° C.

The efficiently nucleated propylene polymers are particularly suitablefor use tubes, pipes and fittings, as well as in buffer tubes of opticalcables.

More specifically, the polymer according to the present invention ischaracterized by what is stated in the characterizing part of claim 1.

The process according to the present invention for preparing nucleatedpolypropylene compositions is characterized by what is stated in thecharacterizing part of claim 6.

The present polymer articles are characterized by what is stated in thecharacterizing parts of claims 34 and 42.

The invention achieves a number of considerable advantages, some ofwhich were already discussed above. In particular it can be noted thatthe present high-crystallinity propylene polymers are characterized byhigh crystallinity and high crystallization temperature. In comparisonto conventional polypropylene the present polymers exhibit goodmechanical properties, such as high modulus, high heat resistance andwater vapour barrier. Very good and consistant nucleation improvesclarity in a better way than with conventional nucleating agents.Nucleation dominates effect from different pigments; this meansconsistent shrinkage and warpage in multicoloured parts. Thecrystallinity is influenced by the high isotacticity (preferably>98%) ofthe polymer and by the effective nucleation with the polymerised vinylcompounds.

With the aid of high polymerization temperatures, the activity of thecatalyst is increased by about 80%. Thus, to mention an example, byusing a transesterified MgCl₂ supported TiCl₄ catalyst preparedaccording to FI 88047 and dicyclopentyl dimethdxy silane (also known asdonor D) as an external electron donor (in the following this catalystis also abbreviated BC-1/D), after a one hour polymerization, theactivity of the catalyst presently used at a polymerization temperatureof 90° C. was about 80 kg/g cat, whereas at 70° C. the activity of thesame catalyst was less than 45 kg/g cat.

The present compositions can be used in any kind of polymer articles.Particular advantages are obtained by applying the compositions to themanufacture of appliances, automotive parts, cups, pails, containers,caps or closures. The new material can also be used in various cable,tube and pipe applications. These are, for example, fiber optic buffertubes, smooth solid wall pipes, fittings, and pipe system details, e.g.valves, chambers and manholes, for indoor or buried sewage, multilayerpipes and fittings for indoor or buried sewages, and structured wallpipes and fittings for buried sewage.

The material used according to the present invention will in a costeffective way give pipes with clearly higher stiffness than standardheterophasic copolymers, measured on plaques of the material itself oron pipes, and improved or retained impact properties. The combination ofhigh HDT and high. stiffness means that it is possible to reduce wallthickness and by this optimize cycle time. Compared to mineral filledPP, the present products provide low cost due to reduced volume price(lower density). Better scratch resistance and high gloss is alsoobtained. The stiffness of polypropylene pipes is increased not only inradial direction but also in axial direction. Furthermore, the pressureresistance (Slow Crack Growth Properties) is improved compared tostandard polypropylene which leads to better long term properties.

Not only do the present propylene polymers render the products excellentmechanical properties, some of which are discussed above, butpreliminary trials indicate that they also improve pipe extrusion byyielding higher output and better pipe surfaces than conventionalpolypropylene having a similar molar mass distribution (MWD) ofhomopolymer phase and rubber phase. In connection with injectionmoulding, faster cycle times for fittings can be obtained.

A further important advantage of the invention resides in the fact thatthe present polymers will achieve low-cost formulations, which makes itpossible to reach about the same final cost per length of pipe as withPVC. In particular, by adding small amounts of talc the stiffness of thepolypropylene compositions can be further improved which reduces PP rawmaterial costs of the final products.

Next, the invention will be more closely examined with the aid of thefollowing detailed description.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A shows the cross-section of an optical fibre buffer tubeaccording to the present invention;

FIG. 1B depicts the cross-section of an optical cable containing aplurality of the present optical fibres; and

FIG. 2 discloses in a schematical fashion an extrusion process forproducing buffer tubes.

DETAILED DESCRIPTION OF THE INVENTION

Definitions

“Strongly coordinating donor” designates donors which form relativelystrong complexes with catalyst surfaces, mainly with a MgCl₂ surface inthe presence of aluminium alkyl and TiCl₄. The donor components arecharacterized by strong complexation affinity towards catalyst surfacesand a sterically large and protective hydrocarbon (R′). Strongcoordination with MgCl₂ requires oxygen-oxygen distance of 2.5 to 2.9 Å[Albizzati et al., Macromol. Symp. 89 (1995) 73-89].

By “Melt Flow Rate” or abbreviated “MFR” is meant the weight of apolymer extruded through a standard cylindrical die at a standardtemperature in a laboratory rheometer carrying a standard piston andload. MFR is a measure of the melt viscosity of a polymer and hence alsoof its molar mass. The abbreviation “MFR” is generally provided with anumerical subindex indicating the load of the piston in the test. Thus,e.g., MFR₂ designates a 2.16 kg load and MFR₁₀ a load of 10.0 kg. MFRcan be determined using, e.g., by one of the following tests: ISO 1133C4, ASTM D 1238 and DIN 53735.

For the purpose of the present invention, “slurry reactor” designatesany reactor, such as a continuous or simple batch stirred tank reactoror loop reactor, operating in bulk or slurry and in which the polymerforms in particulate form. “Bulk” means a polymerization in reactionmedium that comprises at least 60 wt-% monomer. According to a preferredembodiment the slurry reactor comprises a bulk loop reactor.

“Gas phase reactor” means any mechanically mixed or fluid bed reactor.Preferably the gas phase reactor comprises a mechanically agitated fluidbed reactor with gas velocities of at least 0.2 m/sec.

“High temperature polymerization” stands for polymerization temperaturesabove a limiting temperature of 80° C. which is usually known to beharmful for high yield catalysts of related prior art. At hightemperatures the stereospecificity of the catalyst and the morphology ofthe polymer powder can be lost. This does not take place with theparticularly preferred type of catalysts used in the invention which isdescribed below. The high temperature polymerization takes place abovethe limiting temperature and below the corresponding criticaltemperature of the reaction medium. Preferably the high temperaturepolymerization according to the present invention is carried out in aloop reactor.

Nucleation of Propylene Polymers

By nucleating propylene polymers with vinyl compounds it is possible toprovide polypropylene having a higher degree of crystallinity, a highercrystallization temperature, smaller crystallization size and: a greatercrystallization rate. These kinds of compositions can be used for thepreparation of moulded products. They exhibit improved optical andphysical properties.

The nucleation of the propylene polymers can be carried out bymodification of the polymerization catalyst with polymerised vinylcompounds and using the modified catalyst for polymerization ofpropylene optionally in the presence of comonomers to provide apropylene polymer or copolymer containing about 0.0001 to 1%, preferably0.0001 to 0.1% and in particular about 0.001 to 0.01% (calculated fromthe weight of the composition) polymerized vinyl compounds. Anotherapproach for nucleating propylene polymers comprises blendingpolypropylene with polymers containing vinyl compound units.

For the purpose of the present invention “vinyl compounds” are compoundshaving the formula

wherein R₁ and R₂ together form a 5 or 6 membered saturated orunsaturated or aromatic ring or they stand independently for a loweralkyl comprising 1 to 4 carbon atoms.

The following specific examples of vinyl compounds can be mentioned:vinyl cycloalkanes, in particular vinyl cyclohexane (VCH), vinylcyclopentane, vinyl-2-methyl cyclohexane and vinyl norbornane,3-methyl-1-butene, styrene, p-methyl-styrene, 3-ethyl-1-hexene ormixtures thereof. VCH is a particularly preferred monomer but, forexample 3-methyl-1-butene can be used as a monomer or comonomer toadjust the crystallisation temperature.

For the purpose of the present invention “nucleated propylenehomopolymer” stands for a homopolymer (or the homopolymer matrix of ablock copolymer) having an increased and controlled degree ofcrystallinity preferably amounting to over 50% and preferably having acrystallization temperature which is at least 7° C., preferably at least10° C. and in particular over 13° C. higher than the crystallizationtemperature of the corresponding non-nucleated polymer. Using high-yieldZiegler-Natta catalysts, the crystallization temperature of a nucleatedpropylene polymer is higher than 120° C., preferably over 124° C. and inparticular over 126° C. In compositions containing colouring pigmentshaving a nucleating effect, particularly advantageous results areobtained by using polymers having a crystallization temperature over 15°C. higher than that of the corresponding non-nucleated polymer (for apolymer produced with the above-mentioned ZN-catalyst, 128° C.).

According to a preferred embodiment of the present invention,modification of the catalyst with the polymerised vinyl compound, suchas VCH, is performed in an inert fluid which does not dissolve thepolymer formed (e.g. polyVCH). One particularly preferred modificationmedium comprises a viscous substance, in the following a “wax”, such asan oil or a mixture of an oil with a solid or highly viscous substance(oil-grease). The viscosity of such a viscous substance is usually 1,000to 15,000 cP at room temperature. The advantage of using wax is that thecatalyst can be modified, stored and fed into the process in the samemedia and catalyst wax preparation and modification is performed in thesame process device. Due to the fact that no washing, drying, sievingand transferring thus are needed, the catalyst activity is maintained(cf. Finnish Patent No. 95387). The present process is inexpensivebecause high catalyst concentrations and high PP production capacitiescan be used. Also the amount of waste is diminished because themodification medium does not have to be removed.

In the catalyst modification, the polymerization of the vinyl compoundis continued until the concentration of unreacted vinyl compounds isless than about 0.5 wt-%.

A particularly preferred embodiment of the catalyst modificationcomprises the following steps:

introducing a catalyst into the reaction medium;

adding a cocatalyst;

feeding a vinyl compound to the agitated reaction medium at a weightratio of 0.1 to 2, preferably 0.1 to 1.5, vinyl compound/catalyst;

subjecting the vinyl compound to a polymerization reaction in thepresence of said catalyst at a temperature of 35 to 65° C.; and

continuing the polymerization reaction until a maximum concentration ofthe unreacted vinyl compound of less than 2000, preferably less than1000 ppm by weight, is obtained.

According to another preferred embodiment, the method for improving thecrystallinity and transparency of polypropylene by blending acrystalline polypropylene with a vinyl cycloalkane polymer is carriedout by melt-kneading the crystalline polypropylene with the crystalnucleating agent, compounding the crystal nucleating agent with thecrystalline polypropylene and melt kneading the mixture during filmformation, and compounding the master batch of the crystal nucleatingagent with the crystalline polypropylene. Another method of making aconcentrated modified catalyst is to polymerise propylene with themodified catalyst until a predetermined polypropylene-to-pVCH ratio isreached.

The vinyl compound units of the blending and compounding process can bederived from any of the units identified in the above formula 1 inconnection with the first embodiment of the invention.

The modification of the catalyst is carried out essentially before anyprepolymerization of the catalyst with an olefinic monomer, such asethylene or propylene. Prepolymerization here means a conventional,usually continuous process step performed prior to the mainpolymerization step(s), wherein the catalyst is polymerised witholefin(s) to a minimum degree of 10 g polyolefin per 1 g of catalyst. Bycarrying out the modification of the catalyst essentially beforecontacting the catalyst with an olefin, it can be ensured that thepolymerization reaction of the vinyl compound is complete under thereaction conditions observed.

Catalyst

As catalyst any stereospecific catalyst for propylene polymerization canbe used, which is capable of catalyzing polymerization andcopolymerization of propylene and comonomers at a pressure of 5 to 100bar, in particular 25 to 80 bar, and at a temperature of 40 to 110° C.,in particular 60 to 110° C. Preferably the catalyst comprises ahigh-yield, Ziegler-Natta-type catalyst which can be used at highpolymerization temperature of 80° C. or more.

Generally, the Ziegler-Natta catalyst used in the present inventioncomprises a catalyst component, a cocatalyst component, an externaldonor, the catalyst component of the catalyst system primarilycontaining magnesium, titanium, halogen and an internal donor.

The catalyst preferably contains a transition metal compound as aprocatalyst component. The transition metal compound is selected fromthe group of titanium compounds having an oxidation degree of 3 or 4,vanadium compounds, zirconium compounds, chromium compounds, cobaltcompounds, nickel compounds, tungsten compounds and rare earth metalcompounds, titanium trichloride and titanium tetrachloride beingparticularly preferred.

Examples of suitable catalyst systems are described in, for example,Finnish Patents Nos. 86866, 96615 and 88047 and 88048.

One particularly preferable catalyst, which can be used in the presentinvention, is disclosed in FI Patent No. 88047. Another preferredcatalyst is disclosed in Finnish Patent Application No. 963707.

A catalyst system useful in the present process can be prepared byreacting a magnesium halide compound with titanium tetrachloride and aninternal donor. The magnesium halide compound is, for example, selectedfrom the group of magnesium chloride, a complex of magnesium chloridewith a lower alkanol and other derivatives of magnesium chloride. MgCl₂can be used as such or it can be combined with silica, e.g. by absorbingthe silica with a solution or slurry containing MgCl₂. The lower alkanolused can be preferably methanol or ethanol, particularly ethanol.

The titanium compound used in the preparation of the procatalyst ispreferably an organic or inorganic titanium compound, having anoxidation state of titanium of 3 or 4. Also other transition metal.compounds, such as vanadium, zirconium, chromium, molybdenum andtungsten compounds can be mixed with the titanium compound. The titaniumcompound usually is halide or oxyhalide, an organic metal halide, or apurely metal organic compound, in which only organic ligands have beenattached to the transition metal. Particularly preferable are thetitanium halides, especially TiCl₄. Preferably the titanation is carriedout in two or three steps.

The alkoxy group of the phthalic acid ester used comprises at least fivecarbon atoms, preferably at least 8 carbon atoms. Thus, as the ester canbe used for example propyihexyl phthalate, dioctyl phthalate, dinonylphthalate, diisodecyl phthalate, di-undecyl phthalate, ditridecylphthalate or ditetradecyl phthalate.

The partial or complete transesterification of the phthalic acid estercan be carried out e.g. by selecting a phthalic acid ester—a loweralcohol pair, which spontaneously or with the aid of a catalyst, whichdoes not damage the procatalyst composition, transesterifies thecatalyst at an elevated temperatures. It is preferable to carry out thetransesterification at a temperature, which lies in the range of 110 to150° C., preferably 120 to 140° C. Complete transesterification isadvantageous for highly stereospecific catalysts.

The catalyst prepared by the method above is used together with anorganometallic cocatalyst and with an external donor. Generally, theexternal donor has the formula IV

R_(n)R′_(m)Si(R″O)_(4-n-m)

wherein

R and R′ can be the same or different and they stand for a linear,branched or cyclic aliphatic, or aromatic group;

R″ is methyl or ethyl; n is an integer 0 to 3; m is an integer 0 to 3;and n + m is 1 to 3.

The aliphatic groups in the meanings of R and R′ can be saturated orunsaturated. Linear C₁ to C₁₂ hydrocarbons include methyl, ethyl,propyl, butyl, octyl and decanyl. As examples of suitable saturatedbranched C₁₋₈ alkyl groups, the following can be mentioned: isopropyl,isobutyl, isopentyl, tert-butyl, tert-amyl and neopentyl. Cyclicaliphatic groups containing 4 to 8 carbon atoms comprise, e.g.,cyclopentyl, cyclohexyl, methyl cyclopentyl and cycloheptyl.

According to the present invention, the donors used are preferablystrongly coordinating donors which form relatively strong complexes withcatalyst surface, mainly with MgCl₂ surface in the presence of aluminiumalkyl and TiCl₄. The donor components are characterised by a strongcomplexation affinity towards catalyst surface and a sterically largeand protective hydrocarbon (R′).

Typically this kind of donors has the structure of the general formulaII

R′″_(n)Si(OMe)_(4-n)

wherein R′″ is a branched aliphatic or cyclic or aromatic group, and nis 1 or 2, preferably 2. [Härkönen et al., Macromol. Chem. 192 (1991)2857-2863].

Another group of such donors are 1,3-diethers having the formula III

R′R″C(COMe)₂

wherein R′ and R″ are the same or different and stand for a branchedaliphatic or cyclic or aromatic group.

In particular, the external donor is selected from the group consistingof dicyclopentyl dimethoxysilane, diisopropyl dimethoxysilane,di-isobutyl dimethoxysilane, and di-t-butyl dimethoxysilane.

An organoaluminum compound is used as a cocatalyst. The organoaluminiumcompound is preferably selected from the group consisting oftrialkylaluminium, dialkyl aluminium chloride and alkyl aluminiumsesquichloride.

Polymerization

Following the modification of the catalyst with the vinyl compound ofthe first preferred embodiment of the invention, the catalyst isoptionally prepolymerized with propylene and/or another 1-olefin toprovide a prepolymerized catalyst composition which is used forpolymerization of propylene optionally together with comonomers.

The propylene homo- or copolymer can have a unimodal or bimodal molarmass distribution. The MWD is advantageously>4, preferably>6. Thus, theequipment of the polymerization process can comprise any polymerizationreactors of conventional design for producing propylene homo- orcopolymers. The polymerization reactor system can comprise one or moreconventional stirred-tank slurry reactors, as described in WO 94/26794,or one or more gas phase reactors. Preferably the reactors used areselected from the group of loop and gas phase reactors and, inparticular, the process employs at least one loop reactor and at leastone gas phase reactor. This alternative is particularly suitable forproducing bimodal polypropylene. By carrying out the polymerization inthe different polymerization reactors in the presence of differentamounts of hydrogen, the MWD of the product can be broadened and itsmechanical properties and processability improved . It is also possibleto use several reactors of each type, e.g. one loop reactor and two orthree gas phase reactors or two loops and one gas phase reactor, inseries.

The particularly preferred embodiment of the invention comprisescarrying out the polymerization in a process comprising loop and gasphase reactors in a cascade where the loop reactor operates in liquidpropylene and at high polymerization temperatures. The secondpolymerization step is made in gas phase reactor(s) in order to broadenthe molar mass distribution of the polymer.

In every polymerization step it is possible to use also comonomersselected from the group of ethylene, propylene, butene, pentene, hexeneand alike as well as their mixtures.

As emphasized above, the polymerization is carried out at highpolymerization temperatures. With transesterified high-yieldZN-catalysts, these temperatures will increase the isotacticity of thepolymers. At 80 to 90° C., a transesterified catalyst, preparedaccording to FI 88047, together with a strongly coordinating externaldonor, dicyclopentyl-dimethoxysilane, give high yield and low xylenesolubles values of less than 1.5% compared to 2 to 2.5% at 70° C.

The excellent mechanical properties of the present polymers are evidenceby the unique combination of high tensile moduli (E-modulus>2,000 MPa)and impact strength values of about 4 kJ/m² of propylene homopolymers.

In addition to the actual polymerization reactors used for producing thepropylene homo- or copolymer, the polymerization reaction system canalso include a number of additional reactors, such as pre- and/orpostreactors. The prereactors include any reactor for pre-polymerizingthe modified catalyst with propylene and/or other 1-olefin(s), ifnecessary. The postreactors include reactors used for modifying andimproving the properties of the polymer product (cf. below). Allreactors of the reactor system are preferably arranged in series.

The gas phase reactor can be an ordinary fluidized bed reactor, althoughother types of gas phase reactors can be used. In a fluidized bedreactor, the bed consists of the formed and growing polymer particles aswell as still active catalyst come along with the polymer fraction. Thebed is kept in a fluidized state by introducing gaseous components, forinstance monomer on such flowing rate which will make the particles actas a fluid. The fluidizing gas can contain also inert carrier gases,like nitrogen and also hydrogen as a modifier. The fluidized gas phasereactor can be equipped with a mechanical mixer.

The gas phase reactor used can be operated in the temperature range of50 to 115° C., preferably between 60 and 110° C. and the reactionpressure between 5 and 50 bar and the partial pressure of monomerbetween 2 and 45 bar.

The pressure of the effluent, i.e. the polymerization product includingthe gaseous reaction medium, can be released after the gas phase reactorin order optionally to separate part of the gaseous and possiblevolatile components of the product, e.g. in a flash tank. The overheadstream or part of it is recirculated to the reactor.

The propylene homo- or copolymer produced preferably has a MWD of over 2to 10 and a MFR₂ in the range of 0.01 to 1500 g/10min, preferably 0.05to 500 g/10 min.

In the second embodiment of the invention, wherein a uni- or bimodalpropylene homo- or copolymer is blended and compounded with a polymercomprising vinyl compound units, the blending is carried out as known inthe art using said nucleating polymeric agent.

By means of both embodiments, a propylene homopolymer or the homopolymermatrix of a copolymer is produced having high stiffness, an increasedoverall degree of crystallization and a crystallization temperaturemeasured with DSC of more than 7° C., preferably over 10° C. and inparticular 13° C. higher than that of the corresponding non-nucleatedpolymer. The degree of crystallization for the propylene homopolymer isgenerally over 48%, often over 50%, and the elasticity modulus is about2,000 MPa or more. The elasticity modulus of block copolymers containingabout. 12 wt-% of a rubbery component is about 1,500 MPa or more.

The amount of the nucleating polymeric agent is, in case of polymerizedvinyl compounds, about 0.0001 to 1 wt-%, and in case of polypropyleneblends about 0.0001 to 0.5 wt-%, typically below 0.1 wt-% andpreferably<0.01 wt-%.

If desired, the polymerization product can be fed into a gas phasereactor in which a rubbery copolymer is provided by a (co)polymerizationreaction to produce a modified polymerization product. Thispolymerization reaction will give the polymerization product, comprisinge.g. a propylene-ethylene block copolymer, properties of improved impactstrength. The step of providing an elastomer can be perfomed in variousways. Thus, preferably an elastomer is produced by copolymerizing atleast propylene and ethylene into an elastomer. The conditions for thecopolymerization are within the limits of conventional EPM productionconditions such as they are disclosed, e.g., in Encyclopedia of PolymerScience and Engineering, Second Edition, Vol. 6, p.545-558. A rubberyproduct is formed if the ethylene repeating unit content in the polymerlies within a certain range. Thus, preferably, ethylene and propyleneare copolymerized into an elastomer in such a ratio that the amorphouspart of the copolymer contains from 10 to 70% by weight of ethyleneunits. In particular, the ethylene unit content is from 30 to 50% byweight of the amorphous part of the copolymer propylene/ethyleneelastomer. In other words, ethylene and propylene are copolymerized intoan elastomer in a molar ratio of ethylene-to-propylene of 30/70 to50/50. Polymers modified by adding the rubbery copolymer in a gas phasereactor are typically called polypropylene block copolymers orheterophasic copolymers.

The elastomer can also be provided by melt blending a ready-made ornatural elastomer to the polymer product containing no elastomer made ina postreactor.

The amount of a rubbery component can vary in wide ranges, beingpreferably about 5 to 30 wt-%, more preferably about 10 to 20 wt-%.

Polymer Compositions

The present polymers and copolymers of propylene can be blended andoptionally compounded with adjuvants, such as additives, fillers andreinforcing agents conventionally used in the art and/or with otherpolymers. Thus, suitable additives include antioxidants, acidscavengers, antistatic agents, flame retardants, light and heatstabilizers, lubricants, nucleating agents, clarifying agents, pigmentsand other colouring agents including carbon black. Fillers such as talc,mica, calcium carbonate and wollastonite can also be used.

The colouring agent used in the present invention can be any colouringpigment, organic or inorganic. As explained in more detail in ourcopending patent application, by dominating the nucleating effect, ifany, of the pigment, the nucleated propylene homo- or copolymer willprovide a controlled and predictable shrinkage irrespective of thepigment. Examples of colouring pigments are white pigments, such astitanium dioxide, yellow/orange pigments such as isoindolinone orazocondensation, red/violet such as quinacridone or diketo pyrrolopyrol, blue/green pigments such as ultramarine blue or Cu Phtalocyanineblue, and black pigments such as carbon black. Pigments giving a tint(translucent moulded products) can also be considered. The amount ofpigments is usually 0.01 to 5% by weight of the polypropylene component.

According to a preferred embodiment, the present propylene polymers areblended and optionally compounded with a propylene polymer manufacturedwith an unmodified catalyst, or with another polymer, in particular apolyolefin selected from the group of LD-, LLD-, MD- andHD-polyethylenes and polybutylene.

The reinforcing agents suitable for use in the present invention can beselected from chopped or continuous glass fibres, carbon fibres, steelfibres and cellulose fibres.

With reference to the fillers, as described in our copending patentapplication, the addition of talc in amounts of 0.1 to 10 wt-% willprovide particularly interesting advantages. Thus, it increases thestiffness of the propylene polymer composition by up to 5%. Talc inpolypropylene compositions gives rise to higher tensile modulus thantalc in standard PP copolymer. The Heat Deflection Temperature (HDT) isalso increased by the addition of talk, and the HDT value increases morefor the present polypropylene compositions nucleated with a vinylcompound than for standard PP. The crystallization temperature of thepresent compositions is higher than for standard PP containingcorresponding amounts of talc and for polypropylene compositionsnucleated with a vinyl compound. Although the shrinkage of the presentcompositions is somewhat higher that that of standard PP containing talcit is still within the tolerance limits and the present inventionprovides a unique combination of excellent stiffness (up to 1,600 MPa ormore), controlled shrinkage and high T_(cr) giving good cycluspotential.

The present blends can be produced by methods known per se, e.g. bymixing the polymer components with the the adjuvants in the desiredweight relationship using a batch or a continuous process. As examplesof typical batch mixers, the Banbury and the heated roll mill can bementioned. Continuous mixers are exemplified by the Farrel mixer, theBuss co-kneader, and single- or twin-screw extruders.

Manufacture of Tubes, Pipes and Fittings

As discussed above, the present homopolymer or copolymer compositionscan be used for the manufacture of moulded articles, in particulararticles processed by moulding and extrusion, in particular by blowmoulding, injection moulding, compression moulding and pipe, sheet orfilm and cable extrusion. Thus, the polymers can be used for themanufacture of automotive parts, appliances, cups, pails, bottles, caps,closures and lids. Considering the appliances, application areas aremainly housings for beverage machines (water kettles, coffee makersetc.), housings for high temperature appliances (irons, toasters, deepfat fryers), level indicators, liquid reservoirs (requiring goodclarity), and aesthetic and hygienic housings for food preparationequipment.

A particularly interesting application comprises the manufacture ofvarious tubes and pipes by extrusion and fittings by injection moulding.These embodiments will be discussed in more detail in the following.

Extrusion of pipes can be made with different kinds of extruders forpolyolefin polymers, e.g. single or double screw extruders. For solidwall pipes preferably a single screw extruder is used with smooth or agrooved inlet section for force feeding. The screw design relates backto the type of inlet section. With a smooth inlet section a conventional3 step screw (conveying, compression and metering) with a compressionratio of, e.g., 1:3 and a screw length of, e.g., 25 D can be used. Forcefeeding screw design have generally a smaller flight depth and lowercompression ratio and a longer screw length, e.g. 30 D. The screws canbe modified in respect of mixing elements or barrier screws for the samepurpose. The polymer melt, melt temperature around 180 to 250° C.,preferably about 210 C., is metered from the screw into the die head,where the pipe is formed. The formed pipe is transferred to a sizingunit, where the pipe is solidified and cooled down. The sizing unitusesvacuum calibration or pressure calibration for correct dimensions of thepipe. Additional water baths can be added to the extrusion line forsolidification and cooling down the formed pipe.

Extrusion of multilayer pipes follows the principle above, but differentpolymer melt streams are feed to the die-head, e.g. by additional singlescrew extruders, and a multilayer pipe is formed for sizing and cooling.A similar principle to the multilayer is used for structured wall pipes,where the outer layer is formed to external ribs, e.g. double wall pipeswith an outside corrugated layer and an inside smooth layer.

Injection moulding of fittings (connection parts, bends, tees, etc.),valve parts, or other assorted parts of the sewage piping system can bemade using a conventional IM machine with an injection part, e.g.extruder melting down the PP polymer and it injects the polymer into themould(s), one or more moulds with or without insertions of cores, i.e.shaping the fitting, and a mould locking part. The mould is designed fora shrinkage of the PP polymer of about 1.0 to 2.5%, in particular about1.5%. The melt temperature for injection can be about 200 to about 260°C., in particular about 240° C. The hold-on pressure of the mould can beabout 40 to about 60% of the injection pressure, with or without profileduring the step-wise pressure reduction. Injection in profile could beused with fittings consisting of different difficult bends or wallthickness variations in the flow channel (fitting part) of the mould.The mould temperature should preferably be in the range of about 40 toabout 60° C. An alternative method is extrusion injection, where themould is filled by extrusion before the injection.

During extrusion the present polymer give excellent output and good pipesurfaces. In particular in comparison to conventional PP, such as thepolymer mentioned in comparative example 3, which is similar in MWD ofhomopolymer phase and rubber phase, an at least 10% higher output can beobtained. A better melt strength is also noticed during extrusion. Thisfeature is highly beneficial for extrusion of PP and it makes, e.g.,higher wall thickness possible. The nucleation also provides fastercooling by faster solidification and higher Tc.

For injection moulded fittings faster cycle times and better surfaceproperties are obtained. As above, the solidification is faster and Tcis higher.

Products and Product Properties

Efficiently nucleated propylene polymers (in the following also “stiffPP”) manufactured as described above have a number applicationsincluding the field of HEVAC. Thus, by using the present polymersthinner pipes and fittings for buried sewage systems, solid wall pipesand fittings, can be made by, e.g., utilizing pipe series S14 instead ofS12.5 or S11.2 to reach stiffness>8 kN/m² or alternatively reachstiffness>6 kN/m² with pipe series S 16. The S-series and correspondingwall thickness are described in ISO 4065.

Generally speaking, the present invention makes it possible to makethinner pipes within a given dimensioning pipe series and thereby tosave material by lower weight/m pipe. The enhanced stiffness ismanifested in both radial and axial directions of the pipe. The latterproperty improves the handling of the pipes and prevents alarge-diameter sewage pipe from axial sagging. The radial stiffness(e.g. stiffness class>8 kN/m²) decreases the deformation of the pipe bysoil pressure and traffic loads which means that, e.g., the laying depthcan be increased and the pipe can be used under heavy traffickedstreets. The present pipes, accordingly dimensioned, can also be used inless favourable soil conditions since for a flexible pipe the horizontalsoil pressure is the force preventing the pipe from collapsing.

The present polymeric materials can also be employed for indoor sewagepipes and fittings, where the stiffness will give a more rigid productwith existing dimensioning. The materials can also be used forstructured-wall sewage pipes, where the increased stiffness can beutilized to decrease the amount of material used for a specificstiffness, i.e. lower weight/m pipe. Also the injection moulded fittingscan be dimensioned with less material for a specific stiffness.

Stiff PP can also be used for multilayer constructions, e.g. 2-5 layeredpipes combining different PP materials, where at least 1 of the layersis stiff PP. It provides high stiffness in combination to good impactproperties and can be combined with other layers (such as non-nucleatedPP) for functional use. These multilayer pipes include structured wallpipes and smooth multilayer pipes for sewage applications.

Stiff PP can be used in filled PP systems to increase the totalstiffness including fillers and non-nucleated PP and to achieve goodimpact properties by the impact enhancement. Filled polymers can be usedas alternatives to non-filled sewage pipes, e.g. in multilayer pipes.The pressure resistance (Slow Crack Growth Properties) is improvedcompared to that of non-nucleated PP, which leads to better long termprperties. This also opens up the opportunity to use the material forpressure pipes and fittings.

The present stiffPP products can also be used in optical fibre cablebuffer tubes. These buffer tubes are commonly made from poly(butyleneterephthalate), PBT. WO Application 96/23239 (Alcatel) discloses abuffer tube for optical fibre cables made from a PP-PE copolymer resinhaving nucleating agents and filler materials dispersed therein. Thenucleating agents are conventional nucleating agents, i.e. inorganicmaterials and salts of mono- or dibasic acids or arylalkyl acids ormetal or aluminium salts of aromatic or alicyclic carboxylic acids usedin amounts of 0.1 to 1 wt-%. According to the present invention bettertransmission and mechanical properties can be obtained by using thepresent polypropylenes which are nucleated with polymerized vinylcompounds. By controlling the crystallinity of polypropylene the qualityof PP buffer tubes can be further improved. Polypropylene nucleated withpolymerized vinyl compounds can be used for all known designs and typesof fibre optic buffer tubes applicable for polypropylene.

An essential difference between the present invention and theabove-mentioned known tubes is that the amount of polymerized vinylcompounds stemming from catalyst residues is below 0.1 wt-ppm andtypically below 0.01 wt-ppm.

An example of the structure of fibre optic buffer tubes is disclosed inFIGS. 1A and 1B. In cross-section, a buffer tube according to thepresent invention comprises an outer skin layer 1 comprising apolypropylene material nucleated according to the invention. Thethickness of the outer layer is generally in the range from 0.01 to 10mm. The core of the tube comprises a number of optical fibres 3completely surrounded by/immersed in a filling compound 2. The fillingcompound is, e.g., a hydrocarbon-based gel or polymer of thixotropiccharacter. The buffer tubes can be fitted into an optical cable asdepicted in FIG. 1B, or any other known strucre of optical cables basedon buffer tubes. In the example depicted in FIG. 1B, the cable comprisesa jacket 4, a strength member 5 (e.g. a metal wire), and a floodingcompound 6. The buffer tubes 1-3 are fitted around the strength member5.

The buffer tubes can be produced as depicted in FIG. 2 by a coextrusionprocess. Thus, the liquid filling compound is pumped 7 under controlledpressure and flow into the centre of an extruder head 9, surroundingcompletely the optical fibre strands 8 which are fed into the extruderhead 9. Nucleated propylene copolymer melt is fed from an extruderthrough an adapter 10 into the head 9, forming a tube around the fillingcompound layer 11. The product 12 from the extruder head is conducted towater cooling and dimensioning.

The preferred buffer tubes according to the invention comprise aheterophasic, impact-modified propylene block copolymer in which thepropylene polymer has been copolymerized with an ethylene and propylenepolymer. Preferably such a block copolymer has a crystallizationtemperature of over 124° C., preferably over 126° C., a tensile modulusof greater than 1400. MPa, preferably greater than 1500 MPa, and axylene soluble fraction at 23° C. of not more than 15 wt-%,preferably<13 wt-%.

EXAMPLES

The following non-limiting examples illustrate the invention.

In the present context (throughout the specification), the followingtest methods were used in characterizing the properties of the polymers:

HDT (heat deflection temperature): ISO 75-2, method B/0,45MPa

Charpy: ISO 179/at room temperature (if no other T mentioned)

Flexural modulus: ISO 178/at room temperature (if no other T mentioned)

Tensile modulus and tensile strength: ISO 527-2

SHI (the shear thinning index) (0/50): is defined as a ratio of the zeroshear viscosity h0 to the viscosity G*=50 kPa. SHI is a measure ofmolecular weight distribution.

XS: Polymer solubles in xylene at 25° C., measured by dissolving thepolymer in xylene at 135° C., and allowing the solution to cool to 25°C. and filtering then the insoluble part out.

AM: Amorphous part, measured by separating the above xylene solublefraction and precipitating the amorphous part with acetone.

Thermal properties:

Melting temperature, T_(m), crystallisation temperature, T_(cr), and thedegree of crystallinity were measured with Mettler TA820 differentialscanning calorimetry (DSC) on 3±0.5 mg samples. Both crystallisation andmelting curves were obtained during 10° C./min cooling and heating scansbetween 30° C. and 225° C. Melting and crystallisation temperatures weretaken as the peaks of endotherms and exotherms. The degree ofcrystallinity was calculated by comparison with heat of fusion of aperfectly crystalline polypropylene, ie., 209 J/g.

Example 1

A high yield MgCl₂ supported TiCl₄ Ziegler-Natta catalyst preparedaccording to Finnish Patent No. 88047 was dispersed into a mixture ofoil and grease (Shell Ondina Oil N 68 and Fuchs Vaseline Grease SW in2:1 oil-to-grease volume ratio). The titanium content of the catalystwas 2.5 wt-%, and the concentration of the catalyst in the. oil/greasemixture was 15 g cat/dm³. Triethylaluminium (TEAL) was added to thecatalyst dispersion in a TEAL to titanium mole ratio of 1.5. After thatvinylcyclohexane (VCH) was added to the reaction mixture, and the VCH tocatalyst weight ratio was 1:1. The reaction mixture was mixed at atemperature of 55° C. until the concentration of unreacted VCH in thereaction mixture was 1000 ppm by weight.

Example 2

Propylene homopolymers were produced in a pilot plant having a,prepolymerization reactor, a loop reactor and a fluid bed gas-phasereactor connected in series. The catalyst used in the polymerizationswas a VCH-modified Ziegler Natta catalyst prepared similarly to Example1, the cocatalyst was triethylaluminum, TEA, and as an external electrondonor dicyclopentyl dimethoxy silane, D, was used.

The VCH-modified catalyst, TEA and the donor were fed to theprepolymerization reactor for prepolymerization with propylene. Afterthe prepolymerization step the catalyst, TEA and the donor weretransferred to the loop reactor where the polymerization in liquidpropylene took place. From the loop reactor the polymer was transferredto the gas phase reactor without flashing the non-reacted monomer andhydrogen between the reactors. Polymerization was continued in the gasphase reactor to which additional propylene and hydrogen were fed.

The polymerization temperature in the loop and in the gas phase reactorswas 70° C. The hydrogen feed was adjusted such that the polymer in theloop reactor had an MFR₂ of 0.04 g/10 min and in the gas phase reactoran MFR₂ amounting to 3.4 g/10 min. The production rate ratio betweenloop and the gas phase reactor was 45/55.

The properties of the polymers made as described above are summarized inTable 1.

Example 3

The polymerization procedure was as described in Example 2.

The polymerization temperature in the loop and in the gas phase reactorswas 80° C. The hydrogen feed was adjusted such that the polymer in theloop reactor had an MFR₂ of 3.6 g/10 min. and in the gas phase reactoran MFR₂ of 7.7 g/10 min. The production rate ratio between loop and thegas phase reactor was 60/40.

The properties of the polymers made as described above are summarized inTable 1.

Example 4

The polymerization procedure was as described in Example 2.

The polymerization temperature in the loop and in the gas phase reactorwas 80° C. The hydrogen feed was adjusted such that the polymer in theloop reactor had an MFR₂ of 0.07 g/10 min. and in the gas phase reactoran MFR₂ of 4.3 g/10 min. The production rate ratio between loop and thegas phase reactor was 28/72.

The properties of the polymers made as described above are summarized inTable 1.

Example 5

The polymerization procedure was as described in Example 2.

The polymerization temperature in the loop and in the gas phase reactorwas 90° C. The hydrogen feed was adjusted such that the polymer in theloop reactor had an MFR₂ of 4.1 g/10 min. and in the gas phase reactoran MFR₂ of 7.2 g/10 min. The production rate ratio between loop and thegas phase reactor was 50/50.

The properties of the polymers made as described above are summarized inTable 1.

TABLE 1 Properties of the polymers Example 2 Example 3 Example 4 Example5 MFR₂ g/10 min 3.4 7.7 4.3 7.2 XS % 1.5 1.5 1.5 1.3 T_(m) ° C. 166.1166.0 165.3 166.2 T_(cr) ° C. 126.1 127.3 127.7 127.5 Crystallinity %53.3 52.9 54.8 55.1 Zero viscosity Pas 18,000 6,570 29,180 5,950 SHI(0/50) 19 7.8 38 7.3 Tensile strength MPa 39.4 39.2 40.2 39.4 Tensilemodulus MPa 2,070 2,030 2,150 2,000 Flexural modulus MPa 1950 1930 20701930 Charpy, notched kJ/m² 4.4 4.2 3.5 4.1 HDT (0.45 MPa) ° C. 110 110115 109

Example 6

A high yield MgCl₂ supported TiCl₄ Ziegler-Natta catalyst preparedaccording to Finnish Patent No. 88047 was dispersed into a mixture ofoil and grease (Shell Ondina Oil N 68 and Fuchs Vaseline Grease SW at a3.2:1 oil/grease volume ratio). The concentration of the catalyst wasabout 181 g cat/I of oil-grease-catalyst mixture. Triethyl-aluminium(TEAL) was added to the catalyst dispersion in a TEAL to catalyst weightratio of (Al/Ti mole ratio 1.5). After that vinylcyclohexane (VCH) wasadded to the reaction mixture, and the VCH to catalyst weight ratio was0.85:1. The reaction mixture was mixed at a temperature of 55° C. untilthe concentration of unreacted VCH in the reaction mixture was<1000ppm-w.

Example 7 (comparative)

A non-transesterified high yield MgCl₂ supported TiCl₄ Ziegler-Nattacatalyst was dispersed into a mixture of oil and grease (Shell OndinaOil N 68 and Fuchs Vaseline Grease SW in 2:1 Oil/grease volume ratio).The concentration of catalyst was about 175 g cat/l ofoil-grease-catalyst mixture.

Example 8 (comparative)

The catalyst in the oil-crease mixture (catalyst mud) obtained fromExample 7, TEAL, cyclohexylmethyldimethoxysilane (donor C) and propylenewas continuously fed to a process consisting of two loop reactors and afluid bed gas phase reactor.

The TEAL and donor C in a 4 w/w ratio was contacted before mixing withthe catalyst mud. After that the mixture was flushed with propylene,containing the desired amount of hydrogen as molecular weight regulatingagent, to a continuous stirred prepolymerisation reactor.

After the prepolymerisation, the reaction mixture. together withadditional propylene and hydrogen was fed to a continuous loop reactorprocess (including two loop reactors) operating at 68° C. The amount ofhydrogen (molecular weight regulater agent) fed into the loop reactorswas controlled in a way that higher molecular weight fraction wasproduced in the first loop reactor and the lower molecular weightfraction respectively in the second loop reactor. The reactor split forthe loop reactors was 51/49%.

The obtained PP homopolymer-propylene slurry containing the catalyst wascontinuously recovered from the second loop reactor to a flashing unitwhere the liquid propylene was vaporised and the remaining solid polymerparticles, containing the active modified catalyst, was further fed to acontinuous fluidised bed gas phase rector where a propylene ethyleneelastomer for impact modification was produced. The gas phase reactoroperated at a temperature of 73.5° C. The desired amount of propyleneand ethylene was continuously fed to the reactor, and the molecularweight of the copolymer produced was controlled with desired amount ofhydrogen. The final polymer was continuously recovered from the gasphase reactor. After purging the unreacted monomers, the requiredstabilisers and other additives were added and the polymer powder waspelletised with an extruder.

The properties of the polymer are indicated in Tables 2 to 5 under theheading “reference”.

Example 9

The modified catalyst in the oil-crease mixture (catalyst mud) obtainedfrom Example 6, TEAL, dicyclopentyldimethoxysilane and propylene wascontinuously fed to process consisting from two loop rectors and a fluidbed gas phase rector.

The TEAL and dicyclopentyldimethoxysilane in a 4 w/wratio Was contactedbefore mixing with the catalyst mud. After that the mixture was flushedwith propylene, containing the desired amount of hydrogen as molecularweight regulating agent, to a continuous stirred prepolymerisationreactor.

After prepolymerisation, the reaction mixture together with additionalpropylene and hydrogen was fed to a continuous loop reactor process(including two loop reactors) operating at a temperature of 68° C. Theamount of hydrogen (molecular weight regulating agent) fed into the loopreactors was controlled in such a way that a higher molecular weightfraction was produced in the first loop reactor and a lower molecularweight fraction in the second loop reactor. The reactor split for theloop reactors was 52/48%.

The resulted PP homopolymer-propylene slurry containing the catalyst wascontinuously recovered from the second loop reactor to a flashing unitwhere the liquid propylene was vaporised and the remaining solid polymerparticles, containing the active modified catalyst, was further fed to acontinuous fluidised bed gas phase rector where a propylene ethyleneelastomer for impact modification was produced. The gas phase reactoroperated at a temperature of 71.5° C. A desired mount of propylene andethylene was continuously fed to the reactor, and the molecular weightof the copolymer produced was adjusted using a selected amount ofhydrogen. The final polymer was continuously recovered from the gasphase reactor. After purging the unreacted monomers, the requiredstabilisers and other additives were added and the polymer powder waspelletised with an extruder.

The properties of the polymer are summarized in Table 2.

Example 10

The modified catalyst in the oil grease mixture (catalyst mud) obtainedfrom Example 6, TEAL, dicyclopentyldimethoxysilane and propylene wascontinuously fed to process consisting from two loop rectors and a fluidbed gas phase rector.

The TEAL and dicyclopentyldimethoxysilane in a 4 w/w ratio was contactedbefore mixing with the catalyst mud. After that the mixture was flushedwith propylene, containing the desired amount of hydrogen as molecularweight regulating agent, to a continuous stirred prepolymerisationreactor.

After the prepolymerisation, the reaction mixture together withadditional propylene and hydrogen was fed to a continuous loop reactorprocess (including two loop reactors) operating at a temperature of 68°C. The amount of hydrogen (molecular weight regulating agent) fed intothe loop reactors was controlled in such a way that a higher molecularweight fraction was produced in the first loop reactor and a lowermolecular weight fraction in the second loop reactor. The reactor splitfor the loop reactors was 52/48%.

The resulted PP homopolymer-propylene slurry containing the catalyst wascontinuously recovered from the loop reactor to a flashing unit wherethe liquid propylene was vaporised and the remaining solid polymerparticles, containing the active modified catalyst, was further fed to acontinuous fluidised bed gas phase rector where a propylene ethyleneelastomer for impact modification was produced. The gas phase reactoroperated at a temperature of 70° C. The desired amount of propylene andethylene was continuously fed to the reactor, and the molecular weightof the copolymer produced was adjusted using selected amount ofhydrogen. The final polymer was continuously recovered from the gasphase reactor. After purging the unreacted monomers, the requiredstabilisers and other additives were added and the polymer powder waspelletised with an extruder.

The properties of the polymer are summarized in Table 2.

TABLE 2 Polymer compositions and properties Sample Reference Example 9Example 10 MFR₂ g/10 min 0.22 0.23 0.22 Total ethylene wt-% 8.6 6.1 5.5Blockiness % 61.3 57.4 57.2 XS 12.6 11.5 AM wt-% 12.2 11.6 10.8 C2 of AMwt-% 37.1 37.8 29.8 IV/AM 3.4 3.1 3.3 T_(cr) of PP ° C. 115.9 126.9126.8 T_(m) of PP ° C. 164.5 165.9 165 dH of PP J/g 74.2 89.4 92.1

Example 11

Using the polymeric materials of Examples 8, 9 and 10 injection mouldedarticles were manufactured. An IM machine KM90/340B, 40 mm screw, max.clamping force 90 ton was used. The machine settings were; barreltemperature profile 240 to 257° C., melt temperature about 258° C.,injection pressure at cavity about 280 bar, hold-on pressure 25 about 70bar, and mould temperature 58 to 62° C. The injection time was 4 s,hold-on time 40 to 45 s, and cooling time 10 to 15 s.

The physical properties are summarized in Table 3.

TABLE 3 Physical properties of injection moulded articles PropertyReference Example 9 Example 10 Tensile Modulus ISO 527 MPa 1210 14601520 Stress at yield ISO 527 MPa 28.3 29.9 31.1 Flexural Modulus ISO 178MPa 1380 1540 1620 Charpy notched ISO 179 (−20° C.) kJ/m² 4.4 4.4 4.3(+23° C.) kJ/m² 35.1 53.7 43.9

As apparent from Table 3, the injection moulded articles according tothe present invention have a tensile modulus and a flexural moduluswhich are over 10 to 20% higher than those of the reference, while theother important physical properties remain unchanged or are improved.

Example 12

Physical Properties of Compression Moulded Plaques

Compression moulded plaques were made from the materials described inExamples 8 to 10 with a Fontijne Press, 4 mm thickness, heating-up time5 min, pre-heating at 210° C. for 5 min (hold), and moulding for 5 minat 210° C. The cooling rate was 15° C./min. Test bars were milled fromthe plaque. The physical properties of the plaques were determined. Theresults are indicated in Table 3.

TABLE 4 Physical properties of compression moulded plaques PropertyReference Example 9 Example 10 Tensile Modulus ISO 527 MPa 1130 14601560 Stress at yield ISO 527 MPa 24.5 24.3 27 Charpy notched ISO 179 (0°C.) kJ/m² 9.5 32.2 12.1 (+23° C.) kJ/m² 63.8 70 67

As apparent, the physical properties of the plaques according to theinvention are superior to those of the reference. In particular itshould be noted that the tensile strength and the impact strength areclearly improved.

Example 13

The materials of Examples 8 to 10 were utilized for the manufacture ofpipes by conventional pipe extrusion. For the determination pressureresistance, OD 32 mm pipes, SDR 11 were produced with a Battenfeld 45 mmsingle screw extruder with grooved feed section. The temperature settingwere: Inlet 57 to 60° C., temperature profile on cylinder 185 to 200°C., and die head including tool at 205 to 210° C. The melt temperaturewas 232 to 233° C. The screw speed was 45 rpm resulting in an out put ofabout 30 kg/h.

The test results of pressure resistance testing appear from Table 5.

TABLE 5 Pressure resistance of pipes Test method EN 921 ReferenceExample 9 Example 10 Temperature Stress Failure time ° C. MPa (h) 20 165.8 21 116 80 4.2 365 355 1063

The data of given in the table clearly indicate the applicability of thepresent materials for pressure pipes.

For the determination of ring stiffness, OD 110 mm pipes were producedwith a 125 mm single screw extruder, temperature profile 190 to.230° C.,inlet zone 30° C., melt temperature about 226° C., screw speed 120 rpm,and an output of 195 to 210 kg/h.

Pipe ring stiffness, according to ISO 9969, and a calculated valuenormalised value for ring stiffness at a thickness of 4.6 mm anddimensioning series S14 (definition in ISO 4065:1996), were determinedand the results are indicated in Table 6:

TABLE 6 Pipe Ring Stiffness Re- Property Method Unit ference Ex. 9 Ex.10 Ring stiffness Constant ISO 9969 kN/m² 5.3 5.9 6.6 Speed Wallthickness mm 4.17 4.15 4.1 Outside diameter mm 110.5 109.9 110.1Normalised RCS, 7.11 8.03 9.32 4.6 mm

Normalised Ring Stiffness Constant Speed is:

Normalised RCS=RCS measured×(S_(n))³/(S_(m))³

S_(n)=4.6 mm

S_(m)=measured wall thickness

The table shows that the ring stiffness can be improved by 10 to 30% bymeans of the invention.

Example 14

The modified catalyst in the oil grease mixture (catalyst mud) obtainedfrom Example 6, TEAL, dicyclopentyldimethoxysilane and propylene wascontinuously fed to process consisting from two loop rectors and a fluidbed gas phase rector.

The TEAL and dicyclopentyldimethoxysilane in a 4 w/w ratio was contactedbefore mixing with the catalyst mud. After that the mixture was flushedwith propylene, containing the desired amount of hydrogen as molecularweight regulating agent, to a continuous stirred prepolymerisationreactor.

After the prepolymerisation, the reaction mixture together withadditional propylene and hydrogen was fed to a continuous loop reactorprocess operating at a temperature of 68° C., The molecular weight ofthe polymer (i.e. MFR₂) was controlled with the amount of hydrogen(molecular weight regulating agent) fed into the loop reactors.

The resulted PP homopolymer-propylene slurry containing the catalyst wascontinuously recovered from the loop reactor to a flashing unit wherethe liquid propylene was vaporised and the remaining solid polymerparticles, containing the active modified catalyst, was further fed to acontinuous fluidised bed gas phase rector where a propylene ethyleneelastomer for impact modification was produced. The gas phase reactoroperated at a temperature of 70° C. The desired amount of propylene andethylene was continuously fed to the reactor, and the molecular weightof the copolymer produced was adjusted using selected amount ofhydrogen. The final polymer was continuously recovered from the gasphase reactor. After purging the unreacted monomers, the requiredstabilisers and other additives were added and the polymer powder waspelletised with an extruder.

The properties of the polymer are summarized in Table 7:

TABLE 7 Polymer composition and properties Sample Unit Properties* MFR2g/10 min  3.5 Density kg/m³ 905 Total ethylene wt.-%  6.0 XS wt.-%  12.0AM wt.-%  11.0 C2 of AM wt.-%  38.0 IV/AM wt.-%  2.8 Tensile stress,yield dl/g  25 Elongation, yield MPa  6.0 Charpy impact, notched kJ/m² 10** (23°) Rockwell R hardness —  87

Example 15

The material of Table 7 was extruded on a Nokia-Maillefer extruder forwire and cable applications having an appropriate w&c applicationcrosshead, and barrier screw with dimension 60 mm×24D. The extrusionprocessing/tooling was following the so called “tubing” principle (cf.FIGS. 1A, 1B).

The buffer tubes were produced in dimensions from 3.0 to 5.0 mm outerdiametre with fibre counts from 12 to 18. The space between fibres andtube wall was filled with a synthetic, PP-compatible filling compound toprevent water penetration into the tube (cf. FIG. 2)

Extruder temperature settings:

Cylinder: 160-230° C., head and tooling: 220-230° C.

screw speed: 30-80 rpm, output rate: 15-40 kgs/h

What is claimed is:
 1. A nucleated propylene polymer containing 0.0001 to 1 wt-% of a polymerized vinyl compound having the formula

wherein R₁ and R₂ together form a 5 or 6 membered saturated or unsaturated or aromatic ring, comprising a propylene homopolymer or a homopolymer matrix of a block copolymer having a xylene soluble fraction at 23° C. of less than 2.5%, a crystallization temperature of over 126° C., and a degree of crystallization of more than 50%, wherein the tensile modulus of the homopolymer or homopolymer matrix is greater than 2,000 MPa, said polymer being produced by polymerization of propylene optionally with comonomers in the presence of a transesterified Ziegler-Natta catalyst system modified with a polymerized vinyl compound and comprising a strongly coordinating external donor, and said polymer containing less than 0.01 wt-ppm of any unpolymerized vinyl compound.
 2. The polymer according to claim 1, comprising a block copolymer containing a homopropylene polymer matrix and further containing a rubbery copolymer, said block copolymer having a tensile modulus of greater than 1400 MPa, with a maximum rubbery content of 15 wt-%.
 3. The polymer according to claims 1 or 2, wherein the polymerized vinyl compound is selected from the group consisting of vinyl cycloalkane, styrene, p-methyl-styrene and mixtures thereof.
 4. A process for preparing a nucleated propylene homopolymer or a homopolymer matrix of a block copolymer having a xylene soluble fraction at 23° C. of less than 2.5%, a crystallization temperature of over 126° C., and a degree of crystallization of more than 50 %, wherein the tensile modulus of the homopolymer or homopolymer matrix is greater than 2,000 MPa, comprising the steps of A. modifying a catalyst system primarily transesterified with a phthalic acid ester—a lower alcohol pair, said catalyst system comprising a catalyst component, a cocatalyst component, and a strongly coordinating external donor, the procatalyst component of the catalyst system containing magnesium, titanium, halogen and an electron donor, by polymerizing a vinyl compound of the formula

wherein R₁ and R₂ together form a 5 or 6 membered saturated or unsaturated or aromatic ring or they stand independently for a lower alkyl comprising 1 to 4 carbon atoms in the presence thereof; and using the modified catalyst composition for polymerization of propylene optionally in the presence of comonomers to provide a nucleated propylene polymer containing 0.0001 to 1 wt-% of said polymerized vinyl compound; or B polymerizing propylene optionally with comonomers in the presence of a catalyst system primarily transesterified with a phthalic acid ester—a lower alcohol pair to provide said propylene polymer, said catalyst system comprising a catalyst component, a cocatalyst component, and a strongly coordinating external donor, the procatalyst component of the catalyst system containing magnesium, titanium, halogen and an electron donor; and blending it with a nucleated polymer of step A.
 5. The process according to claim 4, wherein the polymerized vinyl compound is selected from the group consisting of vinyl cycloalkane, styrene, p-methyl-styrene and mixtures thereof.
 6. The process according to claim 5, wherein the catalyst is modified by carrying out the modification in a medium which does not essentially dissolve the polymerized vinyl compound and by continuing the polymenzation of the vinyl-compound until the concentration of unreacted vinyl compounds is less than about 0.5 wt-%, said modification being carried out essentially before any prepolymerization step of the catalyst with an olefinic monomer.
 7. The process according to claim 6, wherein the catalyst modification is carried out by introducing a catalyst: into the reaction medium; adding a cocatalyst; feeding a vinyl compound to the agitated reaction medium at a weight ratio of 0.1 to 2 vinyl compound/catalyst; subjecting the vinyl compound to a polymerization reaction in the presence of said catalyst at a temperature of 35 to 65° C.; and continuing the polymerization reaction until a maximum concentration of the unreacted vinyl compound of less than 2000 ppm by weight, is obtained.
 8. The process according to claim 6 or claim 7, wherein the reaction medium is selected from the group consisting of a medium selected from the group of isobutane, propane, pentane, hexane or a viscous substance, which is inert to the reactants.
 9. The process according to claim 5, wherein propylene is polymerized in the presence of a catalyst system transesterified with a phthalic acid ester—a lower alcohol pair at a transesterification temperature in the range of 110 to 150° C.
 10. The process according to claim 7, wherein propylene is polymerized in the presence of a catalyst system comprising a procatalyst component, a cocatalyst component, an external donor, the procatalyst component of the catalyst system containing magnesium, titanium, halogen and an internal electron donor, said external donor having the general formula of R_(n)R′_(m)Si(R″O)_(4-n-m) wherein R′ and R can be the same or different and represent branched or cyclic aliphatic, or aromatic groups, R″ is methyl or ethyl, and n and mare 0 or 1 and n+m is 1 or
 2. 11. The process according to claim 10, wherein the external donor is selected from the group consisting of dicyclopentyldimethoxy silane, di-tert-butyldimethoxy silane, diisopropyldimethoxy silane and diisobutyldimethoxy silane.
 12. The process according to claim 4, wherein propylene is polymerized at a temperature in excess of 80° C.
 13. The process according to claim 12, wherein the polymerization at a temperature in excess of 80° C. is carried out in at least one/slurry or gas phase reactor.
 14. The process according to claim 4, wherein propylene is polymerized by subjecting propylene and optionally other olefins to polymerization in a plurality of polymerization reactors connected in series and employing different amounts of hydrogen as a molar mass modifier in at least two of the reactors, so as to provide a high molar mass polymerization product and a low or medium molar mass polymerization product.
 15. The process according to claim 14, wherein the molar mass distribution, MWD, of the propylene homo- or copolymer is greater than
 4. 16. The process according to claim 14 or 15, wherein propylene is polymerized in a reactor cascade comprising at least one loop reactor and at least one gas phase reactor, the loop reactor being operated at a polymerization temperature of 80 to 110° C.
 17. The process to claim 14, wherein the propylene homopolymer produced is fed into a further reactor in which the polymerization product is combined with an elastomer to produce a modified polymerization product.
 18. The process according to claim 17, wherein the modified polymerization product exhibits properties of improved impact strength.
 19. The process according to claim 17 or 18, wherein the elastomer is produced by copolymerizing propylene and ethylene into an elastomer wherein the amorphous part of the propylene/ethylene copolymer contains from 10 to 70% by weight of ethylene units.
 20. The process according to claim 4, wherein a propylene block copolymer is prepared having a crystallization temperature of over 124° C., a tensile modulus of greater than 1400 MPa and a xylene soluble fraction at 23° C. of not more than 15 wt-%.
 21. The process according to claim 4, wherein the propylene polymer is blended and optionally compounded with adjuvants selected from the group consisting of additives, fillers and reinforcing agents.
 22. The process according to claim 21, wherein the additives are selected from the group consisting of antioxidants, acid scavengers, antistatic agents, flame retardants, light and heat stabilizers, lubricants, nucleating agents, clarifying agents, pigments and carbon black.
 23. The process according to claim 21 or 22, wherein the fillers are selected from the group consisting of mica, calcium carbonate, talc and wollastonite.
 24. The process according to claim 21, wherein the polymer is blended with another polymer.
 25. The process according to claim 21, wherein the reinforcing agent is selected from the group consisting of chopped or continuous glass fibres, carbon fibres, steel fibres and cellulose fibres.
 26. Polymer articles produced by a process according to claim 4, further comprising a step of moulding or extruding.
 27. The polymer articles according to claim 26, wherein the moulding or extruding step is injection moulding, compression moulding, thermoforming, blow moulding or foaming.
 28. The polymer articles according to claim 26 or 27, wherein the polymer articles are sheets, films, cups, pails, bottles, automotive parts, appliances, caps, closures or lids.
 29. Polymer pipes or fittings, comprising a nucleated propylene polymer according to claim
 1. 30. Pipes or fittings according to claim 29, wherein the polymerized vinyl compound is selected from the group consisting of vinyl cycloalkane, styrene, p-methyl-styrene and mixtures thereof.
 31. Pipes or fittings according to claim 29 or claim 30, wherein the nucleated propylene polymer exhibits a Melt Flow Rate (MFR₂, ISO 1133, 230° C., 2.16 kg) of 0.05 to 5 g/10 min, a T_(cr) of over 7° C. higher than the T_(cr) of the corresponding non-nucleated polymer, a crystallinity of over 48%, and a MWD>4.
 32. Pipes or fittings according to claim 31, wherein the nucleated propylene homopolymers and the homopolymer matrix of a heterophasic copolymers exhibit a xylene soluble fraction at 23° C. of less than 2% and a tensile modulus greater than 2000 MPa.
 33. Pipes or fittings according to claim 29, comprising a heterophasic propylene copolymer having a crystallization temperature of over 124° C., a tensile modulus of greater than 1400 MPa, a xylene soluble fraction at 23° C. of not more than 15 wt-%, and an impact strength at 0° C. greater than 7 kJ/m², and at −20° C. greater than 3 kJ/M².
 34. Pipes or fittings according to claim 29, comprising multilayered wall structures, wherein at least one of the walls comprises a non-nucleated propylene polymer.
 35. Pipes or fittings according to claim 34, wherein the walls comprise 2 to 5 layers.
 36. Pipes or fittings according to claim 29, suitable for non-pressure sewage or pressure applications.
 37. Buffer tube for optical fibre cables, comprising a nucleated propylene polymer according to claim
 1. 38. The buffer tube according to claim 37, wherein the propylene polymer is copolymerized with an ethylene and propylene polymer to form an heterophasic impact-modified copolymer.
 39. The buffer tube according to claim 37 or claim 38, comprising a heterophasic propylene block copolymer having a crystallization temperature of over 124° C., a tensile modulus of greater than 1400 MPa, and a xylene soluble fraction at 23° C. of not more than 15 wt-%.
 40. The polymer according to claim 3, wherein the vinyl cycloalkane is selected from the group consisting of vinyl cyclohexane, vinyl cyclopentane, vinyl-2-methyl cyclohexane and vinyl norbornane.
 41. The process according to claim 5, wherein the vinyl mscycloalkane is selected from the group consisting of vinyl cyclohexane, vinyl cyclopentane, vinyl-2-methyl cyclohexane and vinyl norbornane.
 42. The process according to claim 7, wherein the step of feeding a vinyl compound to the agitated reaction medium is performed at a eight ratio of 01 to 1.5 vinyl compound/catalyst, and the polymerization reaction is continued until a maximum concentration of the unreacted vinyl compound is less than 1000 PPM by weight.
 43. The process according to claim 15, wherein the molar mass distribution, MWD of the propylene homo- or copolymer is greater than
 6. 44. The process according to claim 19, wherein the amorphous part of the propylene/ethylene copolymer contains from 30 to 50% by weight of ethylene units.
 45. The process according to claim 20, wherein the propylene block copolymer is prepared having a crystallization temperature of 126° C. or higher, a tensile modulus of greater than 1500 MPa and a xylene soluble fraction at 23° C. of≦13 wt-%.
 46. The process according to claim 24, wherein said another polymer is a polyolefin selected from the group consisting of LD-, LLD-, MD- and HD-polyethylene and polybutylene.
 47. Pipes or fittings according to claim 30, wherein the vinyl cycloalkane is selected from the group consisting of vinyl cyclohexane, vinyl cyclopentane, vinyl-2-methyl cyclohexane and vinyl norbornane.
 48. Pipes or fittings according to claim 31, wherein the nucleated propylene polymer has an MWD of >10.
 49. Pipes or fittings according to claim 33, wherein the heterophasic propylene copolymer has a crystallization temperature of over 12600, a tensile modulus of greater than 1500 MPa, a xylene soluble fraction at 23° C. of ≦13 wt-%, an impact strength at 0° C. greater than 10 kJ/m², and at −20° C. greater than 4 kJ/m².
 50. The buffer tube according to claim 39, wherein the heterophasic propylene block copolymer has a crystallization temperature of over 126° C., a tensile modulus of greater than 1500 MPa, and a xylene soluble fraction at 23° C. of≦13 wt-%.
 51. A nucleated propylene polymer containing 0.0001 to 1 wt-% of a polymerized vinyl compound having the formula

wherein R₁ and R₂ together form a 5 or 6 membered saturated or unsaturated or aromatic ring, comprising a propylene homopolymer or a homopolymer matrix of a block copolymer having a xylene soluble fraction at 23° C. of less than 2.5%, a crystallization temperature of over 126° C., and a degree of crystallization of more than 50%, wherein the tensile modulus of, the homopolymer or homopolymer matrix is greater than 2,000 MPa, said polymer being produced by polymerization of propylene optionally with comonomers in the presence of a transesterified Ziegler-Natta catalyst system modified with a polymerized vinyl compound and comprising a strongly coordinating external donor, and said polymer containing less than 0.01 wt-ppm of any unpolymerized vinyl compound, wherein the catalyst is modified by carrying out the modification in a medium which does not essentially dissolve the polymerized vinyl compound and by continuing the polymerization of the vinyl compound until the concentration of unreacted vinyl compounds is less than about 0.5 wt-%, said modification being carried out essentially before any prepolymerization step of the catalyst with an olefinic monomer, wherein the catalyst is transesterified with a phthalic acid ester—a lower alcohol pair at a transesterification temperature in the range of 110 to 150° C., and wherein said external donor has the general formula of R_(n)R′_(m)Si(R″O)_(4-n-m)  wherein R′ and R can be the same or different and represent branched or cyclic aliphatic, or aromatic groups, R″ is methyl or ethyl, and n and m are 0 or 1 and n+m is 1 or
 2. 